Anode material and method of manufacturing the same

ABSTRACT

An anode material consisting of non-graphitizable carbon material obtained by baking carbon precursor is disclosed. In this non-graphitizable carbon material, ratio by weight of carbon Ps in stacking structure determined from diffraction peak originating in (002) crystal lattice plane and X-ray diffraction spectrum components on the lower angle side with respect to the diffraction peak originating in the (002) crystal lattice plane of X-ray diffraction spectrum is smaller than 0.59, or stacking index SI thereof is smaller than 0.76. Moreover, average number of carbon layers n ave  in stacking structure is smaller than 2.46. Alternatively, when baking temperature is T° C. and half width at half maximum of peak appearing in the vicinity of 1340 cm -1  in Raman spectrum is HW, the condition expressed below is satisfied. 
     
         HW&gt;138-0.06·T 
    
     This non-graphitizable carbon material is manufactured by allowing carbon precursor which becomes non-graphitizable carbon by baking to undergo heat treatment at temperature 600° C. or more under inactive gas atmosphere of flow rate of 0.1 ml/sec. or more per carbon precursor 1 g, or to undergo heat treatment at temperature 600° C. or more under the atmosphere of pressure less than 50 kPa. At this time, carbon precursor is mounted in a layered form so that the area in contact with the atmosphere is 10 cm 2  or more per 1 Kg.

DESCRIPTION

1. Technical Field

This invention relates to an anode material used in a non-aqueouselectrolyte secondary battery and for doping or undoping lithium, and amethod of manufacturing such an anode material.

2. Background Art

With miniaturization of electronic equipments, realization of highenergy density of battery has been required. To meet with suchrequirement, various non-aqueous electrolyte batteries like so calledlithium battery have been proposed.

However, e.g., in batteries using lithium metal as anode, particularlyin the case where such batteries are caused to be secondary battery,there are following drawbacks. Namely,

(1) 5 to 10 hours are ordinarily required for charging, resulting in thefact that quick charge characteristic is poor.

(2) Cycle life-time is short

These drawbacks all result from lithium metal itself, and are consideredto be caused by change of lithium form, formation of lithium in dendriteform and/or irreversible change of lithium, etc. produced by repetitionof charge/discharge operations.

In view of the above, as one technique for solving these problems, amethod using carbonaceous material as anode is proposed. This methodutilizes the fact that lithium carbon interlayer compound can beelectrochemically formed wise ease. For example, when charge operationis carried out within a non-aqueous electrolyte in the state wherecarbon is used as an anode and compound including lithium is used as acathode, lithium in the cathode is electrochemically doped betweenlayers of anode carbon. The carbon into which lithium is doped in thisway functions as lithium electrode, and lithium in the anode is undopedfrom between carbon layers followed by discharge and is returned intothe cathode.

We have demonstrated in the Japanese Patent Application Laid Open No.252053/1991 publication that, as such carbonaceous material,non-graphitizable carbon material having spacing d₀₀₂ of (002) plane of3.70 angsttoms or more, true density less than 1.70 g/cm³, and noexothermic peak at 700° C. or more in the Differential Thermal Analysis(DTA) in air is excellent in quantity of lithium doped/undoped(hereinafter simply referred to as lithium dope/undope quantitydepending upon circumstances).

Meanwhile, in the above-described non-aqueous electrolyte secondarybattery using carbonaceous material, current capacity (mAh/g) per unitweight of the anode is determined by quantity of lithium doped ofcarbonaceous material. Accordingly, it is desirable that lithium dopequantity is as great as possible as the carbonaceous material(Theoretically, ratio of single Li atom to six carbon atoms is upperlimit). When viewed from the above, while employment of theabove-described carbonaceous material results in a great quantity oflithium being doped as compared to the conventional carbonaceousmaterial, it cannot be said that even such carbonaceous material issufficient.

DISCLOSURE OF THE INVENTION

An object of this invention is to provide an anode material which hasgreat quantity of lithium doped and is capable of sufficient currentcapacity, and a method of manufacturing such an anode material.

In order to attain the above-described object, as the result of the factthat the inventors of this invention repeatedly conducted studies for along time, they have obtained findings that, in non-graphitizable carbonmaterial, ratio by weight of carbon in stacking structure Ps, stackingindex SI, and average number of carbon layers n_(ave) in stackingstructure are restricted so that ratio (percentage) of the portionforming the stacked layer structure is caused to be small, and the halfwidth at half maximum HW of peak in the vicinity of 1340 cm⁻¹ of Ramanspectrum is restricted, whereby an anode material having extremely largecapacity can be obtained. Further, they have found out that suchcarbonaceous material is produced by baking (firing) carbon precursorunder an atmosphere such that volatile component produced incarbonization is removed to the outside of the reaction system.

The anode material of this invention has been completed on the basis ofsuch findings, and is characterized in that this anode material isnon-graphitizable carbon material obtained by baking carbon precursor,and ratio by weight of carbon in stacking structure Ps determined fromdiffraction peak originating in (002) crystal lattice plane, and X-raydiffraction spectrum components on the lower angle side with respect tothe diffraction peak originating in (002) crystal lattice plane of X-raydiffraction spectrum is less than 0.59, or stacking index SI thereof isless than 0.76.

Moreover, the average number of carbon layers n_(ave) in stackingstructure portion determined from diffraction peak plane originating in(002) crystal lattice plane and X-ray diffraction spectrum components onthe lower angle side with respect to the diffraction peak originating in(002) crystal plane of X-ray diffraction spectrum is less than 2.46.

Further, the anode material of this invention is non-graphitizablecarbon material obtained by baking carbon precursor, and when bakingtemperature is T° C. and half width at half maximum of peak appearing inthe vicinity of 1340 cm⁻¹ in Raman spectrum is HW, the conditionexpressed below

    HW>138-0.06·T

is satisfied.

Moreover, a method of manufacturing anode material of this invention ischaracterized in that carbon precursor which becomes non-graphitizablecarbon by baking is caused to undergo heat treatment at temperature of600° C. or more under the inactive gas atmosphere of flow rate of 0.1ml/second or more per carbon precursor lg.

Further, the method of this invention is characterized in that carbonprecursor which becomes non-graphitizable carbon by baking is caused toundergo heat treatment at temperature 600° C. or more under theatmosphere of pressure less than 50 kPa.

Further, the method of this invention is characterized in that, incarrying out heat treatment of carbon precursor, the carbon precursor ismounted in a layer form so that the area in contact with the atmosphereis 10 cm² or more per 1 kg.

Non-graphitizable carbon material in which ratio by weight of carbon instacking structure Ps, stacking index SI, and the average number ofcarbon layers n_(ave) in stacking structure, which are parametersreflecting the ratio (percentage) that carbon atoms take stacked layerstructure in non-graphitizable carbon material satisfy a predeterminedcondition has a lithium dope quantity far greater than ideal lithiumdope quantity 372 mAh/g obtained on the assumption that when such carbonmaterial is used as anode material of lithium non-aqueous electrolytebattery, lithium is doped only between carbon layers of the stackedlayer structure portion. It is considered that this is becausenon-graphitizable carbon material in which the above-mentionedparameters satisfy the predetermined condition has a large number ofmicro (very small) vacancy at site where lithium is doped except forcarbon layer of the stacked layer structure portion.

Such non-graphitizable carbon material is obtained by carbonizing carbonprecursor which becomes non-graphitizable carbon by baking in anatmosphere where volatile component produced in carbonization is removedto the outside of the system of reaction such that heat treatment isconducted at temperature of 600° C. or more under the inactive gasatmosphere of flow rate of 0.1 ml/min or more per carbon precursor 1 g,or under the atmosphere of pressure less than 50 kPa. This is based onthe following reason.

Namely, when the carbon precursor is baked, low molecular paraffin,olefin, or low molecular aromatic family is volatilized from atemperature in the vicinity of 400° C., carbon dioxide, methane andcarbon oxide are volatilized at about 600° C., and hydrogen isvolatilized at a higher temperature. Volatilization of low molecularcompound at a lower temperature is based on cleavage of carbon-oxygenbond, or carbon-carbon single bond in carbonaceous material. Thecarbonaceous material forms olefin or aromatic ring having more stabledouble bond. At a higher temperature, hydrogen is desorbed together withcleavage of carbon-hydrogen bond. As a result, polymerization isdeveloped, and aromatic ring is grown. Elimination of volatile componentto the outside of reaction system in such carbonization process promotesformation of vacancy along diffusion path of the volatile component incarbon material particles. It is unknown that such vacancy forms openedpore or closed pore. However, it is estimated that a vacancy resultingfrom diffusion of molecule has a very small capacity. It is thusconsidered that such vacancy takes the structure which reasonablycontributes to capacity.

As stated above, the anode material of this invention isnon-graphitizable carbon material obtained by baking carbon precursor,and weigh ratio Ps, stacking index SI and average number of carbonlayers n_(ave) in stacking structure determined from diffraction peakoriginating in (002) crystal lattice plane, and X-ray diffractionspectrum components on the lower angle side with respect to thediffraction peak originating in (002) crystal lattice plane of X-raydiffraction spectrum, and half width at half maximum HW of peakappearing in the vicinity of 1340 cm⁻¹ in Raman spectrum are restricted.Accordingly, in the case where such carbon material is used as anodematerial of lithium non-aqueous electrolyte battery, quantity of lithiumdoped far greater than theoretical value can be obtained.

In addition, such anode material is obtained by allowing carbonprecursor which become non-graphitizable carbon by baking to undergoheat treatment at temperature of 600° or more under the inactive gasatmosphere of flow rate of 0.1 ml/min. or more per precursor 1 g, orunder the atmosphere of pressure less than 50 kPa, and any additionaloperation except for manufacturing operations until now such as additionof additive into material is unnecessary. Accordingly, this invention isadvantageous to simplification of manufacturing operation and reductionof cost. Therefore, the industrial value is extremely great.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a characteristic diagram showing curve Icorr (θ) obtained bycorrecting X-ray diffraction spectrum of non-graphitizable carbonmaterial.

FIG. 2 is a characteristic diagram showing curve F(θ) obtained bysubtracting minimum value Ia from the curve Icorr(θ) to multiply it bysin (θ).

FIG. 3 is a characteristic diagram showing Patterson function curveobtained by implementing Fourier transform processing to curve F(θ).

FIG. 4 is a characteristic diagram showing curve I(θ) obtained byallowing X-ray diffraction spectrum to undergo smoothing processing.

BEST MODE FOR CARRYING OUT THE INVENTION

In this invention, in order to obtain anode material having greatlithium dope quantity, non-graphitizable carbon material in which ratioby weight of carbon in stacking structure Ps, stacking index SI andaverage number of carbon layers n_(ave) in stacking structure, which areparameters reflecting the ratio of the portion where carbon atoms takestacked layer structure in non-graphitizable carbon material, satisfythe following condition is used as an anode material: ##EQU1##

Namely, non-graphitizable carbon material means carbon material suchthat graphitization is not easily developed even after undergone hightemperature heat treatment such as 3000° C. In this embodiment, it isassumed that non-graphitizable carbon material indicates carbon materialin which d₀₀₂ value after undergone heat treatment at 2600° C. is 3.40angstroms or more.

Such non-graphitizable carbon material consists of stacked layerstructure portion in which carbon atoms take stacked layer structure andnon-stacked layer structure portion. Here, it is considered that in thecase where non-graphitizable carbon material is used as anode material,lithium is not only doped into between carbon layers of the stackedlayer structure portion, but also is doped into micro (very small)vacancy of disturbed carbon layer of the non-stacked layer structureportion. With respect to vacancy in which volume is too large of verysmall vacancy, lithium is unable to remain therein, so such vacancy donot contribute doping of lithium. However, with respect to very smallvacancy in which volume is reasonably small, lithium can remain therein.Such very small vacancy can contribute to doping of lithium. In the casewhere a large number of very small vacancy stated above exist, lithiumdope quantity far greater than ideal lithium dope quantity 372 mAh/gdetermined on the assumption that lithium is doped only between carbonlayers can be obtained.

When it is assumed that density of non-graphitizable carbon material issubstantially fixed, according as ratio of the non-stacked layerstructure portion becomes greater, i.e., ratio of the stacked layerstructure portion becomes smaller, a larger number of such very smallvacancy of the non-stacked layer structure portion exist.

Non-graphitizable carbon material in which parameters Ps, SI, n_(ave)reflecting ratio of the stacked layer structure portion satisfies theabove-described condition, which is proposed as anode material in thisinvention, is non-graphitizable carbon material in which ratio of thestacked layer structure is small, and includes many very small vacancyat the non-stacked layer structure portion. Accordingly, such largenumber of very small vacancy effectively contribute to doping oflithium. Thus, large lithium dope quantity can be obtained.

Here, parameters Ps, SI, n_(ave) reflecting ratio of the stacked layerstructure portion are determined by carrying out data processing, inaccordance with a predetermined procedure, data obtained fromdiffraction peak originating in (002) crystal lattice plane and spectrumcomponent on the lower angle side with respect to the diffraction peakoriginating in (002) crystal lattice plane of X-ray diffraction spectrumof the non-graphitizable carbon material.

As the data processing method for determining the above-mentionedparameters, there is a method disclosed formerly in R. E. Franklin [ActaCryst., 3, 107 (1950)], and also partially described in detail in H. P.Klug and L. E. Alexander, X-ray diffraction Procedures, p. 793 (JohnWiley and Sons, Inc.). This method is applied in Shiraishi, Sanada,Bulletin of Chemical Society of Japan, 1976, No. 1, p.153, Ogawa,Kobayashi, Carbon, 1985, No. 120, p-28, and M. Shiraishi, K. Kobayashi,Bulletin of Chemical Society of Japan, 46, 2575, (1973), etc., and iswidely recognized.

In this invention, SI, Ps, n_(ave) are determined by a simple methodwhich is in conformity with the method disclosed in the above-mentionedliteratures, but is partially simplified for carrying it out moreeasily.

The data processing procedure of the simple method will be describedbelow.

(1) Initially, X-ray diffraction spectrum of non-graphitizable carbonmaterial sample in which SI, Ps and n_(ave) are to be determined isobserved. With respect to the X-ray diffraction spectrum, correction ismade by dividing diffraction intensity I(θ) by squares of polarizationfactor, absorption factor determined by the following formulas (1) and(2) and atomic scattering factor. It is to be noted that while theatomic scattering factor is defined as a function of sin θ/λ, there isused, for obtaining this factor, an approximate value with respect tocarbon atom which is not in valence state described in InternationalTables for X-ray Crystallography, vol. IV, p71 (The kynoch Press, 1974).In addition, diffraction intensity I(θ) may be either X-ray count valueper second or X-ray count value, and is an arbitrary intensity. ##EQU2##In the above-mentioned formulas, A: width when X-ray impinge on thesample surface, which is indicated by A=1·sin β when distance from X-raysource to the sample is 1 and width of divergence slit is β,

t: thickness of sample

μ: linear absorption coefficient of sample given by product of massabsorption coefficient (4.17) and specific gravity of sample

α: half of diffraction angle of monochrometer

(2) Curve Icorr (θ) obtained by correcting X-ray diffraction spectrum isshown in FIG. 1. As seen from FIG. 1, there is a minimum value in thevicinity of 2θ=about 36 degrees in this curve Icorr (θ). This minimumvalue is assumed to be Ia, and peak intensity of peak originating in(002) crystal lattice place is assumed to be Im. In this case, it ispreferable to implement smoothing processing in advance with respect toabout 15 to 35 points in the range of 2θ=15°˜38° for the purpose ofavoiding the influence of noise in signal. Then, by substituting Im, Iadetermined in this way for the following formula (3), SI value isdetermined. ##EQU3##

(3) On the other hand, minimum value Ia is subtracted from curve Icorr(θ) to which no smoothing processing is implemented to multiply thesubtracted value by sin θ to determine intensity F(8). Curve F(θ) thusobtained is shown in FIG. 2.

(4) The curve F(θ) thus obtained is substituted for the followingformula (4) to determine Patterson function. ##EQU4##

This formula (4) is obtained by replacing ordinary Fourier transformformula ∫ F cos(2·π·u·s)·ds (s=2·sin θ/λ) by formula of sum total at θ.The determined Patterson function curve is shown in FIG. 3. As shown,the transform range to the real space of Patterson function is caused tobe broad until reference (value) is sufficiently attenuated. Points ugiving minimum values of the Patterson function curve are assumed to beT₁, T₂, . . . T_(n) in reverse order of magnitude to respectivelydetermine areas p(n) encompassed by straight line and the Pattersonfunction between T_(n) and T_(n+1).

(5) Ratio by weight of carbon in stacks of n layers in stackingstructure, in the non-graphitizable carbon material is determined by thefollowing formula (5) by using p(n). ##EQU5##

In this case, calculation of f(n) indicated by the formula (5) iscarried out up to n which is smaller by one than n when f(n) valuebecomes 0 or negative for the first time.

Then, n_(ave) is determined by the following formula (6) by using thedetermined f(n). ##EQU6##

(6) Then, spacing d₀₀₂ of (002) crystal lattice plane is determined inthe following manner. Namely, with respect to diffraction peakoriginating in the (002) crystal lattice plane cf the X-ray diffractionspectrum observed in (1), smoothing processing of about 15 to 35 pointsis implemented. Curve I(θ) obtained by allowing X-ray diffractionspectrum to undergo smoothing processing is shown in FIG. 4. Then, asshown in FIG. 4, base line is drawn with respect to diffraction peak ofthe curve I(θ) to integrate the portion encompassed by the base line andthe diffraction peak between both contact points of the diffraction peakand the base line. By substituting 2θ just halving the integralintensity for the formula of Bragg, d₀₀₂ is determined.

(7) By using values of n_(ave), SI and d₀₀₂ determined in a manner asdescribed above, ratio by weight of carbon in stacking structure Ps isdetermined by the following formula (7). ##EQU7##

In the above formula, Isp=0.0606·n_(ave) ·d₀₀₂ ²

The data processing procedure for determining SI, n_(ave), Ps has beendescribed. While SI of these parameters is determined by the methodcalled a transmission method, it is not necessarily required todetermine this parameter by this method, but a reflection methodordinarily used may be employed to make correction by suitableabsorption factor, etc. to determine such parameter. In addition, it ispossible to derive parameter which correlates with SI also from valuescorresponding to Im, Ia of uncorrected I(θ) curve although many errorsare included.

Non-graphitizable carbon material in which SI, n_(ave) and Ps determinedin this way satisfy the predetermined condition exhibits high lithiumdope quantity. Further, in this invention, there is also used, as anodematerial, non-graphitizable carbon material in which half width at halfmaximum HW of peak appearing in the vicinity of 1340 cm⁻¹ in Ramanspectrum satisfies the following condition:

    HW>138-0.06·T

Namely, when Raman spectrum is observed with respect tonon-graphitizable carbon material, peaks can be observed in the vicinityof 1340 cm⁻¹ and in the vicinity of 1580 cm⁻¹. The peak in the vicinityof 1580 cm⁻¹ originates in graphite structure in which carbon atoms arestrongly coupled to each other, i.e., the above-described stacked layerstructure portion. On the other hand, the peak in the vicinity of 1340cm⁻¹ originates in phase where symmetrical property is inferior to thatof graphite structure in which carbon atoms are weakly coupled to eachother, i.e., the above-described non-stacked layer structure portion.The half width at half maximum HW of peak in the vicinity of 1340 cm³¹reflects degree of unevenness of coupling state between carbon atoms atthe non-stacked layer structure portion.

It is estimated that in the case where the half width at half maximum HWis greater than 138-0.06·T, unevenness of (coupling state between)carbon atoms in the non-stacked layer structure portion is reasonablygreat and there are a large number of very small pores contributing tolithium doping. In such a case, great lithium dope quantity can beobtained.

It is to be noted that the half width at half maximum of peak in thevicinity of 1340 cm³¹ mentioned here is a value which is one half of avalue ordinarily called half-power band width. Namely, base line isdrawn with respect to peak waveform of Raman spectrum which has beensubjected to fitting to draw a straight line in parallel to base line atthe point where intensity from peak top up to the base line is 1/2.Intersecting points of the peak waveform and the straight line areassumed to be points A, B to read abscissa corresponding to these pointsA, B. Difference between read values of the abscissa corresponding topoints A, B is a half-power band width, and value which is one half ofthe half-power band width is half width at half maximum.

Such non-graphitizable carbon material can be obtained by baking carbonprecursor exemplified below.

Namely, as precursor of the non-graphitizable carbon, there areenumerated material in which functional group including oxygen isintroduced into petroleum pitch, and carbon material in which solidphase carbonization is developed via thermosetting resin, etc.

For example, the above-mentioned petroleum pitch is obtained tar familyobtained by high temperature thermal decomposition such as coal tar,ethylene bottom oil or crude oil, etc. by operation such as distillation(vacuum distillation, ordinary pressure distillation, steamdistillation) thermal polymerization/condensation, extraction, orchemical polymerization/condensation, etc. At this time, H/C atom ratioof petroleum pitch is required to have 0.6˜0.8 in order to allow it tobe non-graphitizable carbon.

Practical means for introducing functional group including oxygen intosuch petroleum pitch is not limited, but, e.g., wet method by aqueoussolution of nitric acid, mixed acid, sulfuric acid or hypochlorous acid,dry method by oxidizing gas (air, oxygen), and reaction by solid reagentsuch as sulfur, ammonium nitrate, ammonium persulfate, or ferricchloride, etc. are used.

Although oxygen percentage content is not particularly prescribed, it ispreferably 3% or more, and is more preferably 5% or more as disclosed inthe Japanese Patent Application Laid Open No. 252053/1991. This oxygenpercentage content affects crystal structure of carbonaceous materialfinally produced. When the oxygen percentage content is caused to be inthe above-mentioned range, there results material having spacing d₀₀₂ of(002) plane of 3.70 angstroms or more, no exothermic peak at atemperature of 700° C. or more in Differential Thermal Analysis (DTA) inair flow, and large anode capacity.

On the other hand, as organic material serving as precursor, phenolresin, acryl resin, vinyl halide resin, polyimide resin, polyamideimideresin, polyamide resin, polyacetylene, conjugate resin such as poly(p-phenylene), etc., cellulose and its derivative, and arbitrary organichigh molecular compound can be used. In addition, condensed polycyclichydro carbon compound such as naphthalene, phenanthrene, anthracene,triphenylene, pyrene, perylene, pentaphene, or pentacene, etc., otherderivatives (e.g., carbonate, carboxylic anhydride, carboxylic imidethereof, etc.), various pitches including mixtures of theabove-mentioned respective compounds as major component, condensedheterocyclic compound such as acenaphthalene, indol, isoindol,quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine,phenazine, phenanthridine, etc., and other derivatives may be used. Inaddition, particularly furan resin consisting of homo polymer orcopolymer of furfuryl alcohol or furfural is also suitable.

Material which undergoes liquid phase carbonization along with heattreatment of the above-mentioned organic materials gives easilygraphitizable carbon. It is sufficient to implement non-fusionprocessing to such organic materials so as to undergo solid phasecarbonization. Namely, it is sufficient to make a device such thatcrosslinking reaction between molecules starts at a temperature lowerthan the temperature at which fusion starts, e.g., there is employed amethod of introducing oxygen included group by a method similar to themethod of implementing processing to the petroleum pitch, a method ofadding chlorine gas or sulphur, or a method of allowing catalyst forpromoting crosslinking reaction to exist, etc.

While carbonaceous material can be obtained by baking the carbonprecursors exemplified above, baking atmosphere in baking carbonprecursor is important in order to obtain carbonaceous material havinggreat lithium dope quantity.

Namely, in this invention, baking of carbon precursor is carried outunder the inactive gas atmosphere of flow rate of 0.1 ml/second percarbon precursor of 1 g, or under the atmosphere of pressure less than50 kPa. When baking of carbon precursor is carried out under theinactive gas atmosphere of flow rate of 0.1 ml/second or more per carbonprecursor of 1 g, volatile component is eliminated by flow of inactivegas. On the other hand, when baking of carbon precursor is carried outunder the low pressure atmosphere of pressure less than 50 kPa,diffusion/desorption of volatile component from the carbon precursor ispromoted, and volatile component is thus efficiently eliminated. Whenbaking of carbon precursor is carried out under an atmosphere such thatvolatile component produced by carbonization is eliminated from theoutside of reaction system, carbonization is smoothly developed. Thus,carbonaceous material having great lithium dope quantity can beobtained.

First, in the case where carbon precursor is baked under the inactivegas atmosphere of flow rate of 0.1 ml/second or more per carbonprecursor of 1 g, inactive gas is gas which does not react oncarbonaceous material at carbonization temperature of 900° C. ˜1500° C.When exemplification is made, this inactive gas is gas including, asmajor component, nitrogen, argon, or mixed gas thereof.

Moreover, at this time, to what degree volatile component is gone isdependent upon not only flow rate of the atmosphere, but also quantityof carbon precursor forwarded to carbonization. Accordingly, in thisembodiment, the flow rate of the atmosphere is prescribed by flow rateper carbon precursor unit weight. When flow rate per carbon precursor 1g is 0.1 ml/second or more, improvement in anode capacity results.

It is to be noted that quantity of carbon precursor indicates totalquantity within furnace in the case of the batch type carbonizationfurnace, and indicates quantity of carbon precursor heated preferably upto 800° C. or more and more preferably up to 700° C. or more in the caseof continuous type carbonization furnace in which carbon precursor isthrown with the passage of time and carbonaceous material is taken outtherefrom.

Further, inactive atmosphere flow rate is caused to be a quantitysufficient to be in contact with carbon precursor heated preferably upto temperature of 800° C. or more and more preferably to temperature of700° C. or more and to be exhausted to the outside of the carbonizationfurnace. Accordingly, flow of the inactive atmosphere with a view toreplacement of the atmosphere within the system before temperature ofcarbonization furnace or carbon precursor is elevated preferably up to800° C. and more preferably up to 700° C. is not included in thisinvention.

It is to be noted that when the area in contact with the atmosphere percarbon precursor 1 g is assumed to be 10 cm² or more in rough surfaceform, carbon precursor is apt to be in contact with inactive gas, sovolatile component is more efficiently removed and development ofcarbonization is more smoothly conducted. In this case, the contact areain rough form mentioned here does not include random very smallunevenness of the material surface, or very small specific surface areawithin particle.

By, e.g., dividing carbon precursor to stack them in multi-stage form,or agitating it (in this case, the specific surface area of carbonprecursor becomes area in contact with the atmosphere), contact area ofcarbon precursor can be broadened.

On the other hand, in the case where carbon precursor is baked under thelow pressure atmosphere of pressure less than 50 kPa, it is sufficientthat pressure under the atmosphere is kept so that it is less than 50kPa at the time when temperature is elevated so that carbonization isattained or at a certain time during temperature elevation. It issufficient that evacuation within carbonization furnace may be carriedout before carbonization furnace or carbon precursor is heated, or inthe process of temperature elevation thereof or for a time period duringwhich temperature at which carbonization is attained is held.

It is to be noted that in the case where carbonization (baking of carbonprecursor) is carried out under any atmosphere, heating system of thecarbonization furnace is not particularly limited, and induction heatingor resistance heating, etc. may be employed for this purpose.

Moreover, arrival temperature and/or temperature elevation speed incarbonization are not particularly limited. For example, afterprovisional baking is carried out at 300°˜700° C. during inactiveatmosphere, regular baking may be carried out under the condition oftemperature elevation speed of 1° C./second or more, arrival temperatureof 900°˜1500° C., holding time at the arrival temperature of about 0 to5 hours during the inactive atmosphere. Of course, provisional bakingoperation may be omitted depending upon circumstances.

Further, carbonaceous material obtained in this way is crushed andsieved so that they are used (applied) as anode material. Such crushingmay be carried out at any time before carbonization, aftercarbonization, or after baking.

An anode consisting of the anode material made up in a manner asdescribed above is accommodated into a battery can along with cathodeand electrolytic solution, and functions as anode of the battery.

Here, since the non-aqueous electrolyte secondary battery of thisinvention aims at attaining high capacity, it is necessary for cathodeto include Li corresponding to charge/discharge capacity of 250 mAh ormore per anode carbonaceous material 1 g in a steady state (after aboutfive times of charge/discharge operations are repeated), it ispreferable to include Li corresponding to charge/discharge capacity of300 mAh or more, and it is more preferable to include Li correspondingto charge/discharge capacity of 350 mAh or more.

It is to be noted that it is not necessarily required that Li isentirely delivered from the cathode material. In a short, it issufficient that Li corresponding to charge/discharge capacity of 250 mAhor more per anode carbonaceous material 1 g exists within the batterysystem. Moreover, it is assumed that quantity of this Li is judged bymeasuring discharge capacity of the battery.

For cathode material constituting the cathode, e.g., compound metaloxide indicated by general expression LIMO2 (M indicates at least onekind of Co and Ni), or interlayer compound including Li is suitable, andsatisfactory characteristic is obtained particularly when LiCoO₂ isused.

Moreover, while non-aqueous electrolytic solution is prepared bysuitably combining organic solvent and electrolyte, any materials whichare used in batteries of this kind may be used as such organic solventand/or electrolyte.

When exemplification is made, as the organic solvent, there arepropylene carbonate, ethylene carbonate, diethyl carbonate, dimethylcarbonate, 1,2-dimethoxy ethane, 1,2 -diethoxy ethane, γ-butyrolactone,tetrahydrofuran, 2- methyl tetrahydrofuran, 1,3 -dioxysolan,4-methy-1,3-dioxysolan, diethyl ether, sulforan, methyl sulforan,acetonitrile, propionitrile, anisole, acetic ester, butyric ester,propionic ester, etc.

As the electrolyte, there are LiClO₄, LiAsF₆, LiPF₆, LiBF₄, LiB(C₆ H₅)₄,CH₃ SO₃ Li, CF₃ SO₃ Li, LiCl, LiBr etc.

This invention will be described below on the basis of practicalexperimental results.

Embodiment 1

First, carbonaceous material was manufactured as follows.

Petroleum pitch (H/C atomic ratio: 0.6˜0.8) was oxidized to preparecarbon precursor of oxygen percentage content of 15.4%. Then, thiscarbon precursor was carbonized at 500° C. for 5 hours in nitrogen gasflow. Then, beads obtained by carbonization were crushed by mill so thatcarbonized material is provided. About 10 g of the carbonized materialwas contained (laid) into crucible. The carbonized material of 10 g laidinto the crucible was baked under the condition of nitrogen gas flow of101/min., temperature elevation speed of 5° C./min., arrival temperatureof 1100° C., and holding time of 1 hour within an electric furnace.Thus, carbonaceous material was obtained. Layer thickness of carbonizedmaterial within the crucible at this time was about 30 mm, and the areain contact with nitrogen gas flow was ˜7 cm².

After the carbonaceous material thus obtained is cooled, it is crushedwithin mortar, and is sieved into particles less than 38 μm by mesh.

With respect to the carbonaceous material, Raman scattering spectrum andX-ray diffraction spectrum were measured. Then, half width at halfmaximum of peak appearing in the vicinity of 1340 cm⁻¹ in Ramanscattering spectrum was determined. Further, data obtained from theX-ray diffraction spectrum was subjected to data processing inaccordance with a predetermined procedure to thereby determine ratio byweight of carbon in stacking structure Ps, stacking index SI and averagenumber of carbon layers n_(ave) in stacking structure.

Half width at half maximum of peak appearing in the vicinity of 1340cm⁻¹ in Raman scattering spectrum was determined as follows.

Initially, Ar⁺ laser beams of wavelength of 514.5 nm and irradiationpower of 200 mW are irradiated to carbonaceous material powder sampleunder the condition of incident beam diameter of 1 mm to convergescattered light pseudo-backward scattering to optically separate theconverged light by using spectrometer to thereby measure Raman spectrum.In the case of this method, since beam diameter of Ar⁺ laser beams forobtaining scattered light is large value of 1 mm, Raman scatteringspectrum measured becomes scattering mean (average value) of a largenumber of carbon material particles existing within the beam diameter.Accordingly, Raman spectrum is measured with high reproducibility andaccuracy.

In this example, double monochrometer manufactured by JOBIN-YVON COMPANYand Trade Name U-1000 was used as the spectroscope (spectrometer). Theslit width is 400-800-800-400 μm.

Four times of Raman scattering spectrum measurements in total wereconducted similarly except that irradiation position is shifted to carryout fitting processing with respect to respective Raman spectrumcomponents. Then, half width at half maximum values of peak in thevicinity of 1340 cm⁻¹ were determined with respect to respectivespectrum components to calculate average value of four half width athalf maximum data to allow the average value thus calculated to be halfwidth at half maximum.

Moreover, X-ray diffraction spectrum was measured by the followingcondition.

    ______________________________________                                        X-ray diffraction measurement condition                                       X ray: CuKα ray (wavelength λ = 1.5418 angstroms)                Measurement device: Trade Name RAD-IIIB by Rigaku sha                         Application voltage and Application current: 40 kV, 30 mA                     Solar slit width: 0.5 degrees                                                 Divergence slit width: 0.5 degrees                                            Reference slit width: 0.15 degrees                                            Sampling interval: 0.05 degrees                                               Scanning speed: 1 degrees/min.                                                Scanning width: 1˜38 degrees at 2θ                                Graphite monochrometer is used                                                (diffraction angle 2α of monochrometer: about                           26.6 degrees)                                                                 Sample filling system:                                                         Sample is filled into opening portion                                         of 5 mm × 18 mm bored at a plate made                                   of SUS of thickness of 0.5 mm so that                                         thickness is equal to 0.5 mm.                                                ______________________________________                                    

HW, Ps, SI, n_(ave) determined by the above-mentioned method andcondition are shown in Table 1.

Moreover, the above-mentioned carbonaceous material was used as anodematerial to make up anode of a coin type battery to measure anodecapacity of the carbonaceous material.

Initially, in order to make up anode, pre-heat treatment was implementedto the carbonaceous material under the condition of temperatureelevation speed of about 30° C./min, arrival temperature of 600° C. andarrival temperature holding time of one hour during the argon atmosphere(It is to be noted this heat treatment was carried out immediatelybefore adjustment of anode mix indicated below). Then, polyvinylidenefluoride corresponding to 10 weight % was added to the carbonaceousmaterial to mix dimethyl formamide as solvent to dry it to prepare anodemix.

The anode mix 37 mg prepared in this way was mixed with nickel meshserving as collector (electricity collecting body) to mold it intopellet of diameter of 15.5 mm thus to prepare anode.

Then, the anode thus made up was assembled into a coin type battery ofthe configuration indicated below to carry out charge/discharge at 1 mA(current density 0.53 mA/cm²) to measure discharge capacity per anodecarbonaceous material 1 g. The configuration and the charge/dischargecondition of the coin type battery were indicated below.

    ______________________________________                                        Configuration of the coin type battery                                        Coin type battery dimensions: diameter 200 mm,                                thickness 2.5 mm                                                              Cathode: Li metal                                                             Separator: porous film (polypropylene)                                        Electrolytic solution:                                                         solution in which LiClO.sub.4 is dissolved                                    into mixed solvent of propylene                                               carbonate and dimethoxyethane (1:1 in                                         terms of volume ratio) with a ratio                                           of 1 mol/l.                                                                  Collector: Copper foil                                                        Charge/Discharge condition                                                    ______________________________________                                    

Charge: current-imposition of one hour and relaxation of two hours wererepeated to extrapolate plot of power of (-1/2) of relaxation timeversus relaxation voltage at times of respective relaxation ofoperations with respect to indefinite time to estimate equilibriumpotential at each charge capacity (intermittent charge/dischargemethod). Charge was assumed to be completed when this equilibriumpotential reaches 2 mV against the lithium electrode.

Discharge: current-imposition of one hour and relaxation of two hoursare repeated similarly to the chargeoperation to complete discharge atthe time point when the battery voltage is below 1.5 volts in closedcircuit state.

Since charge/discharge capacity estimated by this method usesequilibrium potential as reference, the charge/discharge capacityreflects the characteristic inherent in the material.

Anode capacity of carbonaceous material measured in this way is shown inTable 1 along with the above-described HW, SI, Ps and n_(ave).

                                      TABLE 1                                     __________________________________________________________________________                                    ANODE                                                               HW   138 -                                                                              CAPACITY                                                Ps  SI  n.sub.ave                                                                         (cm.sup.-1)                                                                        0.06 · T                                                                  (mAg/g)                                       __________________________________________________________________________    EMBODIMENT 1                                                                            0.531                                                                             0.700                                                                             2.437                                                                             76   72   378                                           __________________________________________________________________________

COMPARATIVE EXAMPLE 1

Carbonaceous material was manufactured similarly to the embodiment 1except that baking of carbonized material is not carried out under thenitrogen gas flow. In this example, arrival temperature in baking waschanged in a manner of 1100° C., 1200° C. and 1300° C.

Raman spectrum and X-ray diffraction spectrum were measured with respectto the carbonaceous material thus obtained to determine half width athalf maximum of peak appearing in the vicinity of 1340 cm⁻¹ in the Ramanscattering spectrum to implement a predetermined data processing to dataobtained from the X-ray diffraction spectrum to thereby determine ratioby weight of carbon in stacking structure Ps, stacking index SI andaverage number of carbon layers n_(ave) in stacking structure. Moreover,the carbonaceous material was used as anode material to make up a cointype battery to carry out charge/discharge under the current-imposedcondition of 1 mA with respect to the manufactured coin type battery tomeasure discharge capacity per anode carbonaceous material 1 g. Measuredresults of HW, Ps, SI, n_(ave) and anode capacity were shown in Table 2.

                  TABLE 2A                                                        ______________________________________                                                  BAKING                                                                        TEMPERATURE Ps      SI     n.sub.ave                                ______________________________________                                        COMPARATIVE 1100          0.597   0.755                                                                              2.471                                  EXAMPLE     1200          0.607   0.700                                                                              2.463                                              1300          0.610   0.774                                                                              2.484                                  ______________________________________                                    

                  TABLE 2B                                                        ______________________________________                                                                     ANDOE                                                      HW                 CAPACITY                                                   (cm.sup.-1)                                                                          138 - 0.06 · T                                                                   (mAh/g)                                          ______________________________________                                        COMPARATIVE 64       72          296                                          EXAMPLE 1   55       66          248                                                      51       60          216                                          ______________________________________                                    

As seen from comparison between Tables 1 and 2, the carbonaceousmaterial made up in the embodiment 1 is such that HW, Ps, SI and n_(ave)satisfy the predetermined conditions (HW>138-0.06·T, Ps <0.59, SI<0.76,n_(ave) <2.46), and has large anode capacity of 378 mAh. On thecontrary, the carbonaceous materials made up in the comparative example1 is such that all of HW, Ps, SI, n_(ave) do not satisfy thepredetermined condition, and has smaller anode capacity as compared tothe carbonaceous material of the embodiment 1.

Accordingly, it has been found out from facts as described above thatmethod of carrying out baking of carbon precursor under the inactive airflow atmosphere is such that HW, Ps, SI, n_(ave) satisfy thepredetermined condition, and is effective for obtaining carbonaceousmaterial having large anode capacity.

Embodiment 2

Carbonaceous material was manufactured similarly to the embodiment 1except that quantity of carbonized material laid into the crucible isset to lg in baking carbonized material.

Then, Raman spectrum and X-ray diffraction spectrum were measured withrespect to the carbonaceous material thus obtained to determine halfwidth at half maximum of peak appearing in the vicinity of 1340 cm⁻¹ inthe Raman scattering spectrum to further implement a predetermined dataprocessing to data obtained from the X-ray diffraction spectrum tothereby determine ratio by weight of carbon in stacking structure Ps,stacking index SI and average number of carbon layers n_(ave) instacking structure. Moreover, the carbonaceous material thus obtainedwas used as anode material to make up a coin type battery to carry outcharge/discharge under the current-imposed condition of 1 mA withrespect to the coil type battery thus made up to measure dischargecapacity with respect to anode carbonaceous material 1 g. Measuredresults of HW, Ps, SI, n_(ave) and anode capacity are shown in Table 3.

                                      TABLE 3                                     __________________________________________________________________________                                    ANODE                                                               HW   138 -                                                                              CAPACITY                                                Ps  SI  n.sub.ave                                                                         (cm.sup.-1)                                                                        0.06 · T                                                                  (mAh/g)                                       __________________________________________________________________________    EMBODIMENT 2                                                                            0.525                                                                             0.706                                                                             2.426                                                                             86   72   442                                           __________________________________________________________________________

As seen from the Table 3, with respect to the carbonaceous materialmanufactured by the above-mentioned method, all of HW, Ps, SI andn_(ave) satisfy the predetermined condition, and anode capacity takes avalue of 442 mAh/g greater than that in the case of the carbonaceousmaterial of the embodiment 1.

From facts as described above, it has been found that, in carbonaceousmaterial obtained by baking carbon precursor under the inactive gas flowatmosphere, anode capacity is dependent upon not only flow rate ofinactive air flow in baking carbon precursor, but also quantity ofcarbon precursor to be baked, and according as inactive air flowquantity per carbon precursor 1 g becomes greater, anode capacitybecomes greater value.

Embodiment 3

Carbonaceous material was manufactured similarly to the embodiment 1except that, in baking carbonized material, alumina boat is used inplace of crucible and carbonized material is mounted on the aluminaboat. In this embodiment, layer thickness of carbonized material on thealumina boat was about 10 mm, and the area in contact with nitrogen gasflow was ˜300 cm².

Then, Raman spectrum and X-ray diffraction spectrum were measured withrespect to the carbonaceous material thus obtained to determine halfwidth at half maximum of peak appearing in the vicinity of 1340 cm⁻¹ inRaman scattering spectrum to further implement a predetermined dataprocessing to data obtained from the X-ray diffraction spectrum tothereby determine ratio by weight of carbon Ps, stacking index SI andaverage number of carbon layers n_(ave) in stacking structure. Moreover,the carbonaceous material thus obtained was used as anode material tomake up a coin type battery to carry out charge/discharge under thecurrent-imposed condition of 1 mA with respect to the coin type batterymade up to measure discharge capacity per anode carbonaceous materiallg. Measured results of HW, Ps, SI, n_(ave) and anode capacity wereshown in Table 4.

                                      TABLE 4                                     __________________________________________________________________________                                    ANODE                                                               HW   138 -                                                                              CAPACITY                                                Ps  SI  n.sub.ave                                                                         (cm.sup.-1)                                                                        0.06 · T                                                                  (mAh/g)                                       __________________________________________________________________________    EMBODIMENT 3                                                                            0.499                                                                             0.675                                                                             2.443                                                                             79   72   432                                           __________________________________________________________________________

As seen from Table 4, with respect to the carbonaceous material made upby the above-mentioned method, all of HW, Ps, SI and n_(ave) satisfy thepredetermined condition, and anode capacity takes a value of 432 mAh/ggreater than that in the case of the carbonaceous material of theembodiment 1.

From facts as above, it has been found out that in the carbonaceousmaterial obtained by baking carbon precursor under the inactive gas flowatmosphere, anode capacity is dependent upon layer thickness, i.e.,contact area of carbon precursor in baking the carbon precursor, andaccording as layer thickness of the carbon precursor becomes thin, andthe contact area thereof becomes greater, the anode capacity takes agreater value. This is because volatile component is more satisfactorilygone in the case where layer thickness of carbon precursor becomesthinner.

Embodiment 4

Carbonaceous material was manufactured similarly to the embodiment 1except that, in baking carbonized material, about 10g of the carbonizedmaterial is laid into the crucible to bake it, while keeping pressurewithin electric furnace at about 20 kPa, under the condition oftemperature elevation speed of 5° C./min., arrival temperature of 1100°C., 1200° C. and 1300° C., and holding time at the arrival temperatureof one hour.

Then, Raman spectrum and X-ray diffraction spectrum were measured withrespect to the carbonaceous material thus obtained to determine halfwidth at half maximum of peak appearing in the vicinity of 1340 cm⁻¹ inRaman Scattering spectrum to further implement a predetermined dataprocessing to data obtained from the X-ray diffraction spectrum tothereby determine ratio by weight of carbon Ps, stacking index SI, andaverage number of carbon layers n_(ave) in stacking structure. Moreover,the carbonaceous material was used as anode material to make up a cointype battery to carry out charge/discharge under the current-imposedcondition of 1 mA with respect to the coin type battery thus made up tomeasure discharge capacity per anode carbonaceous material 1 g. Measuredresults of HW, Ps, SI, n_(ave) and anode capacity are shown in Table 5.

                  TABLE 5A                                                        ______________________________________                                                  BAKING                                                                        TEMPERATURE                                                                   (°C.)                                                                              Ps      SI     n.sub.ave                                ______________________________________                                        EMBODIMENT 4                                                                              1100          0.504   0.670                                                                              2.408                                              1200          0.527   0.700                                                                              2.410                                              1300          0.568   0.731                                                                              2.415                                  ______________________________________                                    

                  TABLE 5B                                                        ______________________________________                                                                     ANDOE                                                      HW                 CAPACITY                                                   (cm.sup.-1)                                                                          138 - 0.06 · T                                                                   (mAh/g)                                          ______________________________________                                        EMBODIMENT 4                                                                              88       72          463                                                      79       66          437                                                      70       60          383                                          ______________________________________                                    

COMPARATIVE EXAMPLE 2

Carbonaceous material was manufactured similarly to the embodiment 4except that pressure within the electric furnace is set to 60 kPa inbaking carbonized material.

Then, Raman spectrum and X-ray diffraction spectrum were measured withrespect to the carbonaceous material thus obtained to determine halfwidth at half maximum of peak appearing in the vicinity of 1340 cm⁻¹ inRaman scattering spectrum to further implement a predetermined dataprocessing to data obtained from the X-ray diffraction spectrum tothereby determine ratio by weight of carbon Ps, stacking index SI, andaverage number of carbon layers n_(ave) in stacking structure. Moreover,the carbonaceous material was used as anode material to make up a cointype battery to carry out charge/discharge under the current-imposedcondition 1 mA with respect to the coin type battery thus made up tomeasure discharge capacity per anode carbonaceous material 1 g.

As a result, HW, Ps, SI, n_(ave) and anode capacity of the carbonaceousmaterial of the comparative example 2 are the same order as that in thecase of the comparative example 1, i.e., the above-mentioned parametersdo not satisfy the predetermined condition, and the anode capacity isalso small. On the contrary, in the case of the carbonaceous material ofthe embodiment 4, as seen from the Table 5, HW, Ps, SI, n_(ave) satisfythe predetermined condition, and has an anode capacity far greater thanthat of the carbonaceous material of the comparative example 2.

Accordingly, it has been found out from facts as described above that amethod of baking carbon precursor under the low pressure atmosphereresults in the fact that HW, Ps, SI, n_(ave) satisfy the predeterminedcondition, and is effective for obtaining carbonaceous material havinglarge anode capacity.

Embodiment 5

Carbonaceous material was manufactured similarly to the embodiment 1except that baking of carbonized material is carried out in a mannerdescribed below.

Namely, about 10 g of carbonized material was laid into the crucible tobake it at 900° C. within an enclosed electric furnace. Aftertemperature is lowered, about 10 g was laid into the crucible for asecond time to bake it, while keeping pressure within the electricfurnace at about 20 kPa, under the condition of temperature elevationspeed of 5° C./min., arrival temperature 1100° C., and holding time atthe arrival temperature of one hour. Thus, carbonaceous material wasobtained.

Then, Raman spectrum and X-ray diffraction spectrum were measured withrespect to the carbonaceous material thus obtained to determine halfwidth at half maximum of peak appearing in the vicinity of 1340 cm⁻¹ inRaman spectrum to further implement a predetermined data processing todata obtained from the X-ray diffraction spectrum to thereby determineratio by weight of carbon Ps, stacking index SI, and average number ofcarbon layers n_(ave) in stacking structure. Moreover, the carbonaceousmaterial thus obtained was used as anode material to make up a coin typebattery to carry out charge/discharge under the current-imposedcondition of 1 mA with respect to the coin type battery thus made up tomeasure discharge capacity per anode carbonaceous material 1 g.

As a result, HW, Ps, SI, n_(ave) and anode capacity of carbonaceousmaterial were the same order as that of the carbonaceous material of theembodiment 4. From facts as described above, it has been found out that,in baking carbon precursor under the low pressure atmosphere to obtaincarbonaceous material, even if evacuating operation is carried outbefore carbonization furnace or carbon precursor is heated, or in theprocess of temperature elevation or for a time period during whicharrival temperature is held, HW, Ps, SI, n_(ave) similarly satisfy thepredetermined condition, and carbonaceous material having high anodecapacity is obtained.

COMPARATIVE EXAMPLE 3

Initially, carbonized material was manufactured similarly to theembodiment 1.

About 10 g of carbonized material thus obtained was laid into thecrucible to bake it at 900° C. within an enclosed electric furnace.After temperature is lowered, about 10 g was laid into the crucible fora second time to bake it under the condition of temperature elevationspeed of 5° C./min., arrival temperature of 1100° C., and holding timeat the arrival temperature of one hour within the enclosed electricfurnace. Thus, carbonaceous material was obtained.

Then, Raman spectrum and X-ray diffraction spectrum were measured withrespect to the carbonaceous material thus obtained to determine halfwidth at half maximum of peak appearing in the vicinity of 1340 cm⁻¹ inRaman scattering spectrum to further implement a predetermined dataprocessing to data obtained from the X-ray diffraction spectrum tothereby determine ratio by weight of carbon Ps, stacking index SI, andaverage number of carbon layers n_(ave) in stacking structure. Moreover,the carbonaceous material thus obtained was used as anode material tomake up a coin type battery to carry out charge/discharge under thecurrent-imposed condition of 1 mA with respect to the coin type batterythus made up to measure discharge capacity per anode carbonaceousmaterial 1 g.

As a result, HW, Ps, SI, n_(ave) and anode capacity of carbonaceousmaterial were the same order as that of the carbonaceous material of thecomparative example 1. Also from facts as described above, it has beenfound out that it is important that pressure of the atmosphere is causedto be low at the time of arrival temperature in baking carbon precursorunder the low pressure atmosphere to obtain carbonaceous material.

Embodiment 6

Furfuryl alcohol resin was baked, while keeping pressure within theelectric furnace at about 20 kPa, under the condition of temperatureelevation speed of 5° C./min., arrival temperature of 1200° C., andholding time of one hour. Thus, carbonaceous material was obtained.After the carbonaceous material thus obtained was cooled, it was crushedby mill, and was split into particles less than 38 μm by mesh.

Then, Raman spectrum and X-ray diffraction spectrum were measured withrespect to the carbonaceous material thus obtained to determine halfwidth at half maximum of peak appearing in the vicinity of 1340 cm⁻¹ inRaman scattering spectrum to further implement a predetermined dataprocessing to data obtained from the X-ray diffraction spectrum tothereby determine ratio by weight of carbon Ps, stacking index SI, andaverage number of carbon layers n_(ave) in stacking structure. Moreover,the carbonaceous material thus obtained was used to make up a coin typebattery to carry out charge/discharge under the current-imposedcondition of 1 mA with respect to the coin type battery thus made up tomeasure discharge capacity per anode carbonaceous material 1 g. Measuredresults of HW, Ps, SI, n_(ave) and anode capacity are shown in Table 6.

                                      TABLE 6                                     __________________________________________________________________________                                    ANODE                                                               HW   138 -                                                                              CAPACITY                                                Ps  SI  n.sub.ave                                                                         (cm.sup.-1)                                                                        0.06 · T                                                                  (mAh/g)                                       __________________________________________________________________________    EMBODIMENT 6                                                                            0.570                                                                             0.737                                                                             2.452                                                                             90   66   403                                           __________________________________________________________________________

COMPARATIVE EXAMPLE 4

Carbonaceous material was manufactured similarly to the embodiment 6except that baking of furfuryl alcohol was carried out within anenclosed electric furnace.

Then, Raman spectrum and X-ray diffraction spectrum were measured withrespect to the carbonaceous material thus obtained to determine halfwidth at half maximum of peak appearing in the vicinity of 1340 cm³¹ 1in Roman scattering spectrum to further implement a predetermined dataprocessing to data obtained from the X-ray diffraction spectrum tothereby determine ratio by weight of carbon Ps, stacking index SI, andaverage number of carbon layers n_(ave) in stacking structure. Moreover,the carbonaceous material thus obtained was used as anode material tomake up a coin type battery to carry out charge/discharge under thecurrent-imposed condition of 1 mA with respect to the coin type batterythus made up to measure discharge capacity per anode carbonaceousmaterial 1 g. Measured results of HW, Ps, SI, n_(ave) and anode capacityare shown in Table 7.

                                      TABLE 7                                     __________________________________________________________________________                                    ANODE                                                               HW   138 -                                                                              CAPACITY                                                Ps  SI  n.sub.ave                                                                         (cm.sup.-1)                                                                        0.06 · T                                                                  (mAh/g)                                       __________________________________________________________________________    COMPARATIVE                                                                             0.583                                                                             0.764                                                                             2.475                                                                             65   66   282                                           EXAMPLE 4                                                                     __________________________________________________________________________

As seen from comparison between Tables 6 and 7, the carbonaceousmaterial of the embodiment 6 is such that HW, Ps, SI, n_(ave) havesatisfy the predetermined condition, and has an anode capacity greaterthan that of the carbonaceous material of the comparative example 4. Onthe contrary, the carbonaceous material of the comparative example 4 issuch that HW, Ps, SI, n_(ave) do not satisfy the predeterminedcondition, and has a smaller anode capacity.

From facts as above, it has been found out that this manufacturingmethod is effective also when organic material which becomesnon-graphitizable carbon by baking is used as carbon precursor similarlyto petroleum pitch in which functional group including oxygen isintroduced.

What is claimed is:
 1. An anode material comprising:non-graphitizablecarbon material obtained by baking a carbon precursor, wherein saidmaterial exhibits a portion having a stacking structure and a portionwith a non-stacking structure such that a ratio (Ps) by weight of carbonin said stacking structure portion compared to said non-stackingstructure portion is less than 0.59 or a stacking index (SI) of saidmaterial is less than 0.76.
 2. An anode material as set forth in claim1, wherein an average number of carbon layers (n_(ave)) in said stackingstructure portion is less than 2.46.
 3. An anode material as set forthin claim 1, wherein said ratio is determined from a diffraction peakoriginating in a (002) crystal lattice plane and X-ray diffractionspectrum components on the lower angle side with respect to thediffraction peak originating in the (002) crystal lattice plane of theX-ray diffraction spectrum.
 4. An anode material comprisingnon-graphitizable carbon material produced by baking a carbon precursor,wherein when:a baking temperature is T° C., and a half width at halfmaximum of a peak appearing in the vicinity of 1340 cm⁻¹ in a Ramanspectrum is HW, HW>138-0.06·T.
 5. A method of manufacturing an anodematerial, wherein a carbon precursor which becomes non-graphitizablecarbon when baked is caused to undergo heat treatment at a temperatureof approximately 600° C. or more under an inactive gas atmosphere whichhas a flow rate of 0.1 ml/sec. per 1 gram of said carbon precursor.
 6. Anethod of manufacturing an anode material as set forth in claim 5,wherein, in carrying out said heat treatment, said carbon precursor ismounted in a layer form so that the area in contact with the atmosphereis approximately 10 cm² or more per 1 Kg.
 7. A method of manufacturingan anode material, wherein a carbon precursor which becomesnon-graphitizable carbon when baked is caused to undergo heat treatmentat a temperature of approximately 600° C. or more under an atmospherehaving a pressure of approximately 50 kPa or less.
 8. An anodecomprising non-easily graphitized carbon material obtained by baking acarbon precursor, wherein a weight ratio (Ps) of carbon which takes astacked layered structure, which ratio is obtained from a diffractionpeak originating in a (002) crystal lattice plane and X-ray diffractionspectrum components on the lower angle side with respect to thediffraction peak originating in the (002) crystal lattice plane of X-raydiffraction spectrum, is smaller than 0.59 or a stacking index (SI)thereof is smaller than 0.76.
 9. An anode as set forth in claim 8,wherein an average number of carbon layers (n_(ave)) in said stackedlayer structure as determined from a diffraction peak originating in a(002) crystal lattice plane and X-ray diffraction spectrum components onthe lower angle side with respect to the diffraction peak originating inthe (002) crystal lattice plane of X-ray diffraction spectrum, issmaller than 2.46.
 10. An anode material comprising non-easilygraphitized carbon material wherein when a baking temperature is T° C.and a half width at half maximum of a peak appearing in the vicinity of1340 cm⁻¹ in a Raman spectrum is HW, then HW>138-0.06·T.
 11. An anodematerial comprising:non-graphitizable carbon material, wherein saidmaterial exhibits a portion having a stacking structure and a portionwith a non-stacking structure such that a ratio (Ps) by weight of carbonin said stacking structure portion compared to said non-stackingstructure portion is less than 0.59 or a stacking index (SI) of saidmaterial is less than 0.76.
 12. An anode material as set forth in claim11, wherein an average number of carbon layers (n_(ave)) in saidstacking structure portion is less than 2.46.